JP4977343B2 - Acrylic resin composition and sheet-like molded body using the same - Google Patents

Description

  The present invention relates to an acrylic resin composition and a sheet-like molded body using the same.

  Electronic equipment parts, especially electronic devices, personal computers, etc., generally generate heat during operation, so a metal heat sink or the like is installed in the electronic equipment device to prevent damage to the parts due to heat and to ensure stable operation. Yes. Further, if necessary, the heat sink is forcibly cooled by a fan or the like. Furthermore, forced cooling by water circulation or forced cooling using a Peltier element, which is a kind of semiconductor element, is employed for components that generate large heat.

  When such a cooling device is attached to the heating element, a material called a heat conduction material is used to close the contact between the cooling device and the heating element and to transfer heat to the cooling device effectively. Yes. That is, such a heat conductive material is interposed between the cooling device and the heating element to improve heat transfer between them. As such a heat conductive material, silicone grease, a silicone rubber sheet with increased thermal conductivity, a silicone gel sheet, or the like is generally used from the viewpoints of thermal decomposition stability, flame retardancy, and the like.

  However, silicone grease is difficult to handle because it is a high-viscosity liquid, and it is difficult to control the application amount when applied to heat-generating parts, and the fluidity increases and flows out (pumps out) as the temperature rises. There was a problem. In addition, there is a problem that it is difficult to use substantially because the adhesiveness is not so good on a large uneven surface of a heat generating component. Furthermore, since it is a silicone-based material, a slight amount of siloxane gas is generated, and this siloxane gas adheres to electrode contacts and the like to generate silicon dioxide, which may cause contact failure. There was sex.

  In addition, silicone rubber sheets with higher thermal conductivity and silicone gel sheets with lower hardness cannot be easily manufactured because the silicone resin itself is expensive and may require a vulcanization step in the manufacturing process. There was a problem. Further, since siloxane gas is generated in the same manner as the above-mentioned silicone-based grease, there is a possibility that a contact failure may occur in such a silicone rubber sheet or silicone gel sheet. Moreover, when a heat conductive filler such as a metal oxide is contained in such a silicone rubber sheet in a high ratio, it becomes difficult to form a sheet, and the obtained sheet becomes a brittle sheet.

  In order to solve such problems as silicone grease, silicone rubber sheet, silicone gel sheet, etc., heat conduction such as rubber, urethane, acrylic, etc. containing a heat conductive filler such as alumina, boron nitride, etc. Materials (resin compositions) have been proposed.

  For example, Japanese Patent Laid-Open No. 2002-30212 (Patent Document 1) discloses a heat conductive sheet including an acrylic polyurethane resin and a heat conductive filler dispersed in the acrylic polyurethane resin. Yes. However, in such a conventional sheet-like molded article, since a prepolymerized so-called acrylic polyurethane is used as a resin matrix, it is difficult to form a sheet at the time of production, and the processability is low. There was a problem that the flexibility of the molded body was low.

In JP 2004-161856 (Patent Document 2), an acrylic copolymer containing a carboxyl group as a functional group and a compound containing two or more glycidyl groups in one molecule are used as a matrix. , A composition comprising a thermally conductive filler selected from the group consisting of nitrides, metal oxides or metal powders is disclosed. However, even with the composition described in Patent Document 2, the processability is not always sufficient, and the flexibility of the obtained sheet-like molded product is not always sufficient.
JP 2002-30212 A JP 2004-161856 A

  The present invention has been made in view of the above-described problems of the prior art, can sufficiently suppress the viscosity and improve the processability, and has a high degree of flexibility and can be attached to an electrical component or the like with good adhesion. It aims at providing the acrylic resin composition which can obtain the sheet-like molded object which can be obtained, and the sheet-like molded object obtained using the same.

  As a result of intensive studies to achieve the above object, the inventors of the present invention contain an acrylic copolymer containing a carboxyl group as a functional group and two or more glycidyl groups in one molecule as a functional group. The inventors have found that the above object can be achieved by an acrylic resin composition containing a compound and a specific hardness adjusting agent, and have completed the present invention.

That is, the acrylic resin composition of the present invention includes an acrylic copolymer containing a carboxyl group as a functional group, a compound containing two or more glycidyl groups in one molecule as a functional group as a curing agent , a child containing a compound containing a monofunctional glycidyl groups as hardness modifiers,
The hardness in an amount ranging from 1 to 60% on a mass basis with respect to the calculated amount of the hardness adjusting agent having a functional group ratio calculated by equivalent calculation of 1: 1 for the acrylic copolymer. Containing a conditioner; and
The compound containing a monofunctional glycidyl group as the hardness adjusting agent is an alcohol glycidyl ether or phenyl glycidyl ether having 4 to 15 carbon atoms,
It is characterized by.

  Moreover, in the acrylic resin composition of the present invention, it is preferable to further contain 250 to 500 parts by mass of a thermally conductive filler made of a metal hydroxide with respect to 100 parts by mass of the acrylic copolymer. .

  Moreover, the sheet-like molded body of the present invention is characterized in that the acrylic resin composition of the present invention is molded and cured into a sheet shape.

  ADVANTAGE OF THE INVENTION According to this invention, the acrylic type which can obtain the sheet-like molded object which can suppress a viscosity enough and can improve workability, has a high degree of flexibility, and can be stuck with sufficient adhesiveness to an electrical component etc. It becomes possible to provide a resin composition and a sheet-like molded body obtained by using the resin composition.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  First, the acrylic resin composition of the present invention will be described. That is, the acrylic resin composition of the present invention includes an acrylic copolymer containing a carboxyl group as a functional group, a compound containing two or more glycidyl groups in one molecule as a functional group, and a hardness regulator. And a compound containing a monofunctional glycidyl group.

  The acrylic copolymer according to the present invention contains a carboxyl group as a functional group in the molecule. A method for producing such an acrylic copolymer is not particularly limited. For example, a vinyl monomer and a carboxyl that are copolymerizable mainly with an acrylic monomer having no functional group. A method of simultaneously polymerizing (copolymerizing) a monomer having a group, a method of copolymerizing an acrylic monomer having a carboxyl group and another acrylic monomer, polymerizing a monomer copolymerizable with an acrylic monomer, A method of performing a terminal termination reaction with a group-containing molecule can be employed.

  Examples of the acrylic monomer having no functional group include methyl acrylate (methyl acrylate), ethyl acrylate (ethyl acrylate), propyl acrylate (propyl acrylate), and iso-propyl acrylate (acrylic acid-iso-propyl). ), N-butyl acrylate (acrylic acid-n-butyl), iso-butyl acrylate (acrylic acid-iso-butyl), tert-butyl acrylate (acrylic acid-tert-butyl), 2-ethylhexyl acrylate (acrylic acid) -2-ethylhexyl), octyl acrylate (octyl acrylate), iso-octyl acrylate (acrylic acid-iso-octyl), decyl acrylate (decyl acrylate), iso-decyl acrylate (isodecyl acrylate) ), Iso-nonyl acrylate (acrylic acid-iso-nonyl), neopentyl acrylate (neopentyl acrylate), tridecyl acrylate (tridecyl acrylate), lauryl acrylate (lauryl acrylate) and other alkyl acrylates; Alicyclic alkyl acrylates such as xyl acrylate, isobornyl acrylate, tricyclodecyl acrylate, tetrahydrofurfuryl acrylate; methyl methacrylate (methyl methacrylate), ethyl methacrylate (ethyl methacrylate), propyl methacrylate (propyl methacrylate), iso -Propyl methacrylate (methacrylic acid-iso-propyl), n-butyl methacrylate (methacrylic acid-n-butyl), iso-butyl methacrylate Rate (methacrylic acid-iso-butyl), tert-butyl methacrylate (methacrylic acid-tert-butyl), 2-ethylhexyl methacrylate (methacrylic acid-2-ethylhexyl), octyl methacrylate (octyl methacrylate), iso-octyl methacrylate (Iso-octyl methacrylate), decyl methacrylate (decyl methacrylate), isodecyl methacrylate (isodecyl methacrylate), isononyl methacrylate (isononyl methacrylate), neopentyl methacrylate (neopentyl methacrylate), tridecyl methacrylate (methacrylic acid) Tridecyl), methacrylic acid alkyl esters such as lauryl methacrylate (lauryl methacrylate); cyclohexyl methacrylate, isobornyl And alicyclic alkyl methacrylates such as dimethacrylate, tricyclodecyl methacrylate, and tetrahydrofurfuryl methacrylate.

  Among the acrylic monomers having no functional group, alkyl acrylates and alkyl methacrylates are preferably used. In particular, n-butyl acrylate (acrylic acid-n-butyl), 2-ethylhexyl acrylate ( It is preferable to use 2-ethylhexyl acrylate).

  Examples of the vinyl monomer include acrylonitrile, acrylamide, methacrylamide, N-dimethylacrylamide, N-dimethylmethacrylamide, N-dimethylaminoethyl acrylate, N-dimethylaminoethyl methacrylate, N-diethylaminoethyl acrylate, N-diethylamino. Examples include ethyl methacrylate, vinyl acetate, styrene, α-methylstyrene, divinylbenzene, and allyl (meth) acrylate.

  Furthermore, as the monomer having a carboxyl group as the functional group, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid or functionalities derived from these monomers And monomers.

  Further, the polymerization method is not particularly limited, and a known method can be appropriately employed. For example, an emulsion polymerization method (emulsion polymerization method), a suspension polymerization method (suspension polymerization method), a bulk polymerization method (bulk) A polymerization method such as method) can be employed.

  In addition, the acrylic copolymer obtained in this way can be utilized for various uses, such as a molded object, an adhesive, a coating material, a fiber, a sealing agent.

  The carboxyl group of the acrylic copolymer according to the present invention may be present at the molecular end or in the middle of the molecular chain, and may be present either on the side chain or on the main chain. The acrylic copolymer according to the present invention may be a random copolymer or a block copolymer. The structure of the acrylic copolymer used in the present invention is not limited to a single structure, and it is also possible to use a mixture of acrylic copolymers of various repeating units.

  Furthermore, as the acrylic copolymer according to the present invention, in addition to the acrylic copolymer obtained by copolymerizing two or more kinds of monomers obtained as described above, different acrylic homopolymers are mixed together. A mixture of an acrylic homopolymer and an acrylic copolymer, or a mixture of acrylic copolymers can be used.

  In addition, among the components constituting the acrylic copolymer according to the present invention, the glass transition temperature (Tg) of at least the main component polymer is −60 ° C. to −20 ° C. as measured by the DSC method. The glass transition temperature of all polymers is more preferably −60 to −20 ° C. If the glass transition temperature of such a main component polymer is too high, the resulting acrylic resin composition tends to be hard.

  In addition, the molecular weight of the acrylic copolymer according to the present invention is preferably a number average molecular weight calculated by polystyrene conversion by gel permeation chromatography (GPC) measurement is 800 to 20000, and preferably 2000 to 15000. More preferred. When the molecular weight is less than 800, extremely low molecular weight substances (monomers, dimers, trimers, etc.) are likely to be present in the polymer, and not only bleed out when cured, but also voids occur during curing. On the other hand, when the molecular weight exceeds 20000, the fluidity of the polymer is lowered and the workability is inferior, and it is difficult to add an appropriate amount of the heat conductive filler.

  Moreover, it is preferable that the acid value (AV) by the potassium hydroxide (KOH) titration is 20 to 150, and the ratio of the carboxyl group in the acrylic copolymer according to the present invention is 50 to 150. It is more preferable. When such an acid value is less than 20, the heat resistance and flame retardancy of the sheet-like molded product obtained by lowering the crosslinking density tend to decrease. On the other hand, when the acid value exceeds 150, the resulting acrylic The crosslink density of the sheet-like molded product obtained by molding the resin composition is too high, and the flexibility (flexibility) tends to decrease.

  The viscosity of the acrylic copolymer is preferably 90000 mPa · s or less under conditions of a pressure of 1013 hPa and a temperature of 25 ° C. When the viscosity exceeds 90000 mPa · s, the fluidity of the polymer is lowered, and it becomes difficult to add and disperse the heat conductive filler, and the workability tends to be lowered. The viscosity used in the present specification is a value measured with a Brookfield BH rotational viscometer. When the acrylic copolymer exhibits thixotropic flow, the viscosity is preferably 90000 mPa · s or less when the shear rate is increased, and when it exhibits dilatant flow, the shear rate is extremely low shear. Also preferred are those having a viscosity of 90000 mPa · s or less.

  Furthermore, from the viewpoint of more surely preventing the generation of voids when producing a sheet-like molded body as described later, the acrylic copolymer is one that does not substantially contain a solvent component. It is preferable.

  A compound having two or more glycidyl groups in one molecule as a functional group according to the present invention plays a role as a curing agent in the present invention. That is, the compound having a glycidyl group can react with the carboxyl group of the acrylic copolymer to give a cured product.

  Various compounds having two or more glycidyl groups in one molecule can be used. For example, sorbitol polyglycidyl ether (SORPGE), polyglycerol polyglycidyl ether (PPGGE), pentaerythritol polyglycidyl ether ( PETPGE), diglycerol polyglycidyl ether (DGGGE), glycerol polyglycidyl ether (GREPGE), trimethylolpropane polyglycidyl ether (TMMPGE), resorcinol diglycidyl ether (RESDGE), neopentyl glycol diglycidyl ether (NPGDGE), 1, 6-hexanediol diglycidyl ether (HDDGE), ethylene glycol diglycidyl ether (EGDGE), polyethylene glycol Coal diglycidyl ether (PEGDGE), propylene glycol diglycidyl ether (PGDGE), polypropylene glycol diglycidyl ether (PPGDGE), polybutadiene diglycidyl ether (PBDGE), diglycidyl phthalate (DGEP), halogenated neopentylglycerol diglycidyl Examples include ether, bisphenol A type diglycidyl ether (DGEBA), bisphenol F type diglycidyl ether (DGEBF), and trimethylolpropane polyglycidyl ether (TMMPGE), sorbitol polyglycidyl ether (SORPGE) and the like are particularly preferably used. be able to.

Moreover, it is preferable that the epoxy equivalent (WPE) of the compound which has a 2 or more glycidyl group in 1 molecule as a functional group concerning this invention exists in the range of 80-400. When the epoxy equivalent exceeds 400, the required performance of the sheet-like molded product obtained by adding a large amount of the compound to react with the acrylic copolymer tends to be insufficient, If the epoxy equivalent is less than 80 , the reaction rate tends to be too high, and it tends to be difficult to produce a sheet-like molded product.

  Further, such a compound having two or more glycidyl groups in one molecule is preferably in a liquid state under conditions of a pressure of 1013 hPa and a temperature of 25 ° C.

  Further, as such a compound having two or more glycidyl groups in one molecule, the weight loss value after heating for 10 minutes at 150 ° C. under a pressure of 1013 hPa is 3 with respect to the weight before heating. It is preferable that the solvent is substantially free of solvent so as to be not more than%. When such a weight loss value by heating exceeds 3%, the contained solvent tends to hinder the reaction, making it difficult to produce a sheet-like molded article. Furthermore, a sheet from which the contained solvent can be obtained. This is because bubbles are generated inside the shaped molded body. In addition, as a calculation method of such a heating weight reduction value, when the sample 5g was heated for 10 minutes on 150 degreeC temperature conditions under normal pressure (1013 hPa) using the HG53 type | mold halogen moisture meter by a METTLER TOLEDO Co., Ltd. A method is used in which the change in weight is measured and the reduction rate is calculated by comparing the weight before and after heating.

  The hardness adjusting agent according to the present invention is a compound containing a monofunctional glycidyl group. The hardness adjusting agent according to the present invention has a role of adjusting the crosslinking density between the acrylic copolymer containing a carboxyl group as the functional group and the compound containing two or more glycidyl groups in one molecule. To fulfill. That is, in the present invention, in a resin comprising an acrylic copolymer containing a carboxyl group as the functional group described above and a compound containing two or more glycidyl groups in one molecule as described above, By containing the hardness adjusting agent, it becomes possible to impart sufficient flexibility to the acrylic resin composition and the molded body thereof.

  As the compound containing a monofunctional glycidyl group used as a hardness adjusting agent in the present invention, a glycidyl ether of an aliphatic hydrocarbon or aromatic hydrocarbon containing a monofunctional glycidyl group such as alcohol glycidyl ether or phenyl glycidyl ether, Fatty acid glycidyl ester containing monofunctional glycidyl group such as epoxidized fatty acid octyl ester, stearyl glycidyl ester, glycidyl acrylate or glycidyl methacrylate, 1,2-epoxybutane 1,2-epoxyhexane, 1,2-epoxydecane, 1, Epoxy compounds or monofunctional groups of saturated hydrocarbons containing monofunctional glycidyl groups such as 2-epoxycyclohexane, 1,2-epoxy-5-hexene, and 1,2-epoxy-5,9-cyclooctadiene. Examples thereof include epoxidized products of unsaturated hydrocarbons containing ricidyl groups, epoxidized products of polysiloxanes containing monofunctional glycidyl groups, and mixtures thereof.

  Among such compounds containing a monofunctional glycidyl group, it is preferable to use alcohol glycidyl ether or phenyl glycidyl ether having 4 to 20 (more preferably 10 to 15) carbon atoms. When the alcohol glycidyl ether has a carbon number of less than 4, when a sheet-like molded article is produced, the hardness modifier tends to precipitate on the surface because the molecular weight is small, and a bleedout over time tends to occur. On the other hand, when the number of carbons exceeds 20, the reactivity becomes slow and the role as a hardness adjusting agent is not fulfilled, and the flexibility of the sheet-like molded product tends to decrease when the sheet-like molded product is produced. It is in. In addition, since the phenyl glycidyl ether has higher reactivity and has a large effect as a hardness adjusting agent, a sheet-like molded body was produced using phenyl glycidyl ether as a hardness adjusting agent. In such a case, the flexibility of the sheet-like molded product tends to be further improved.

Moreover, it is preferable that the epoxy equivalent (WPE) of the hardness adjusting agent concerning this invention exists in the range of 100-300. When the epoxy equivalent exceeds 300, a large amount of the compound containing the monofunctional glycidyl group is added to react the compound containing the monofunctional glycidyl group according to the present invention with the acrylic copolymer. In the obtained sheet-like molded article, the required performance tends not to be sufficiently achieved. On the other hand, when the epoxy equivalent is less than 100 , the monofunctional glycidyl group-containing compound and the acrylic copolymer The reaction rate with the coalescence tends to be too fast, making it difficult to produce a sheet-like molded product.

  Furthermore, as such a hardness adjusting agent, a solvent whose substantial weight loss value after heating for 10 minutes at 150 ° C. under a pressure of 1013 hPa is 3% or less with respect to the weight before heating is substantially used. It is preferable that it does not contain. When such a weight loss value by heating exceeds 3%, the contained solvent tends to hinder the reaction, making it difficult to produce a sheet-like molded article. Furthermore, a sheet from which the contained solvent can be obtained. This is because bubbles are generated inside the shaped molded body. In addition, as a calculation method of such a heating weight reduction | decrease value, the method similar to the calculation method of the heating weight reduction | decrease value of the compound which has two or more glycidyl groups in the above-mentioned molecule | numerator is employ | adopted.

  Further, in the acrylic resin composition of the present invention, the hardness adjusting agent is such that the content of the hardness adjusting agent is such that the functional group ratio calculated by equivalent calculation with respect to the acrylic copolymer is 1: 1. It is preferable that the amount is in the range of 1 to 60% (more preferably 1 to 13%) on the mass basis with respect to the calculated amount of Further, when the content of the hardness adjusting agent relative to the calculated amount is less than 1% on a mass basis, sufficient flexibility can be imparted to a sheet-like molded body obtained by reducing the effect of imparting flexibility as a hardness adjusting agent. On the other hand, if it exceeds 60% on a mass basis, it becomes difficult to cure the resulting acrylic resin composition, so that the suitability for sheeting and the like tends to decrease.

  Moreover, as content of the compound which contains two or more glycidyl groups in 1 molecule as said functional group, an epoxy equivalent exists in the range of 100-300 with respect to the acid equivalent 100 of the said acrylic copolymer. It is preferable. When the epoxy equivalent is less than 100, the heat resistance of the sheet-like molded product obtained by curing does not sufficiently progress during the production of the sheet-like molded product and does not completely solidify, on the other hand, If the epoxy equivalent exceeds 300, the resulting sheet-like molded product will remain unreacted and an excess of the compound containing two or more glycidyl groups in one molecule will cause bleed out over time. Heat resistance also tends to decrease.

  In the acrylic resin composition of the present invention, an acrylic copolymer containing a carboxyl group as the functional group, a compound containing two or more glycidyl groups in one molecule as the functional group, and the hardness adjustment It is preferable to use a compound containing a monofunctional glycidyl group as an agent as a matrix, and to further contain a thermally conductive filler made of a metal hydroxide in the matrix. Such metal hydroxides tend to have higher compatibility with the resin and higher flame retardancy than other thermally conductive fillers.

  Moreover, as such a metal hydroxide, it is preferable to use a metal hydroxide having a decomposition temperature of 250 ° C. or more, and specifically, aluminum hydroxide, magnesium hydroxide, barium hydroxide, calcium hydroxide, etc. A powder can be mentioned. When the decomposition temperature is less than 250 ° C., it tends to be difficult to impart sufficient thermal conductivity to the obtained sheet-like molded body. In addition, the measurement method of the said decomposition temperature measured only the metal hydroxide (thermally conductive filler) by TGA (Thermo Gravimetric Analyzer) by the temperature increase rate of 10 degree-C / min from room temperature to 600 degreeC by the atmospheric condition. The temperature at which the mass starts to decrease is measured and used as the decomposition temperature.

  Moreover, although the magnitude | size, shape, etc. of such a metal hydroxide are not restrict | limited in particular, As a shape of a metal hydroxide, it is preferable that it is spherical or pseudo-spherical.

  Moreover, it is preferable that the average particle diameter of such a metal hydroxide is about 0.5-30 micrometers. If the average particle size is less than 0.5 μm, when the metal hydroxide is contained in the matrix, the viscosity of the liquid becomes too high, and the processability when producing a sheet-like molded product tends to be reduced. On the other hand, when the average particle size exceeds 30 μm, the metal hydroxide is difficult to be mixed into the matrix, and thus tends to be difficult to uniformly disperse.

  Furthermore, as such a metal hydroxide, it is possible to use a combination of metal hydroxides having the same composition but different average particle diameters. Thus, it becomes possible to reduce the viscosity of the acrylic resin composition obtained by combining the metal hydroxide in the matrix by combining several types having different average particle diameters.

  The content of the metal hydroxide (thermally conductive filler) in the acrylic resin composition of the present invention is 250 to 500 parts by mass (more preferably 260 to 600 parts by mass with respect to 100 parts by mass of the acrylic copolymer). 500 parts by mass). By setting it as such addition amount, it exists in the tendency which the heat conductivity and flame retardance of the acrylic resin composition of this invention improve more. Moreover, when the content of the metal hydroxide is less than 250 parts by mass, sufficient flame retardancy and thermal conductivity tend not to be ensured. On the other hand, when the content of the metal hydroxide exceeds 500 parts by mass. Although flame retardancy and thermal conductivity are improved, the viscosity of the resulting acrylic resin composition tends to be high, and the processability when producing a sheet-like molded product tends to be reduced.

  Further, such metal hydroxides can be used in combination with other thermally conductive fillers. As such other thermally conductive fillers, nitrides such as boron nitride and aluminum nitride, metal oxides such as alumina and magnesia, metal powders such as silicon carbide, carbon, copper, silver, and aluminum should be added. Furthermore, it is also possible to add a metal carbonate such as calcium carbonate, which is not necessarily excellent in heat conduction, or a filler such as clay or kaolin.

  Furthermore, in the acrylic resin composition of the present invention, a catalyst, a flame retardant, a wetting and dispersing agent, an antioxidant, a weather stabilizer, a heat stabilizer, etc. are appropriately added according to the required performance of the molded product obtained by molding. It is possible to add, and particularly when the thermal conductive filler is contained, it is preferable to contain a wetting and dispersing agent.

  Such a wetting and dispersing agent has a functional group capable of improving the compatibility with the acrylic copolymer and a functional group capable of adsorbing to the thermally conductive filler (filler). Wetting dispersants are preferred. Examples of such a wetting and dispersing agent include saturated polyester copolymers having boric acid groups and / or phosphoric acid groups, polyhydric alcohol organic acid esters, special alcohol organic acid esters, urethane-modified acrylic copolymers, high molecular weight polyesters, and polycarboxylic acids. Copolymer, grafted product of allyl alcohol, maleic anhydride, styrene copolymer and polyoxyalkylene monoalkyl ether, polyacrylic acid ammonium salt, acrylic copolymer ammonium salt, silicon-based polymer ethylene oxide and / or propylene oxide Examples include adducts. Among such wetting and dispersing agents, it is preferable to use a saturated polyester copolymer having a boric acid group and / or a phosphoric acid group.

  The addition amount of such a wetting and dispersing agent is preferably 0.05 to 3.0 parts by mass with respect to 100 parts by mass of the acrylic copolymer. If the addition amount of the wetting and dispersing agent is less than 0.05 parts by mass, the compatibility between the matrix and the metal hydroxide powder tends to be low and kneading tends to be difficult. If the amount exceeds 3.0 parts by mass, thickening and gelation of the resulting acrylic resin composition occur, and the curability of the composition tends to decrease, making it difficult to produce a sheet-like molded product.

  Examples of the flame retardant include ammonium polyphosphate, expanded graphite, red phosphorus, phosphate ester, ammonium phosphate, boron compound, molybdenum compound, antimony compound, zinc stannate, triazine compound, melamine compound, guanidine compound, hydrotalcite Etc.

  Further, the expanded graphite used as the flame retardant preferably has an expansion temperature of 200 ° C. or higher, more preferably 270 ° C. or higher. When the expansion temperature is less than 200 ° C., the environment in which the sheet-shaped molded body is used may reach a temperature condition of 120 to 150 ° C. at the maximum, so that the sheet-shaped molded body expands due to long-term heating during use. In addition, the acrylic resin composition tends to expand even at the heating temperature when the acrylic resin composition is crosslinked and cured.

  The average particle size of the expanded graphite is not particularly limited, but is preferably about 10 μm to 50 μm from the viewpoint of dispersibility in the matrix and processability. If the average particle diameter of the expanded graphite is less than the lower limit, the expanded graphite powder tends to be easily blown during processing, and the workability tends to be lowered. On the other hand, if the upper limit is exceeded, the flame retardancy tends to be lowered.

Furthermore, the addition amount of the expanded graphite is preferably 20 to 200 parts by mass with respect to 100 parts by mass of the acrylic copolymer. If the amount of the expanded graphite exceeds 200 parts by mass, the thermal conductivity is improved, but the volume resistance of the obtained sheet-like molded product is 10 ¹⁰ Ω or less, so that a short circuit occurs in a circuit such as an electronic device component. In addition, the smoothness of the sheet surface tends to decrease. On the other hand, if the amount of the expanded graphite added is less than 20 parts by mass, the desired flame retardancy tends not to be obtained.

  The acrylic resin composition of the present invention can be produced by measuring and blending each component so as to have the aforementioned content, and mixing and stirring. The method of mixing and stirring is not particularly limited, and can be appropriately selected depending on the composition of the polymer, the viscosity, and the amount of each component added. Specifically, a stirrer such as a dissolver mixer or a homomixer is used. The method to use is mentioned. In addition, when mixing a metal hydroxide, it is also possible to mix a metal hydroxide in advance with a compound containing two or more glycidyl groups in one molecule as the functional group. The mixing and stirring method can also be used in such mixing.

  Moreover, you may filter what was mixed and stirred in this way as needed, for example in order to remove the lump of an undispersed component. By performing such filtration, a homogeneous acrylic resin composition can be obtained, and it becomes possible to efficiently produce a sheet-like molded body. Moreover, it is preferable that bubbles generated in the liquid during such mixing and stirring are defoamed under reduced pressure. By performing such defoaming, it is possible to prevent bubbles from being generated in the sheet-like molded body produced using the resulting acrylic resin composition.

  Next, the sheet-like molded body of the present invention will be described. That is, the sheet-like molded body of the present invention is obtained by molding and curing the above-mentioned acrylic resin composition of the present invention into a sheet shape.

  The method for forming such an acrylic resin composition into a sheet and curing it is not particularly limited, and a known method can be appropriately employed. As such a method, for example, the acrylic resin composition is coated on a base film (polyester film or the like) and cured by heating at 160 to 200 ° C. for 5 to 15 minutes. Can be mentioned.

  The thickness of the sheet-like molded body of the present invention is preferably 0.5 mm to 3 mm, and more preferably 1.0 mm to 2.0 mm. When the thickness is less than 0.5 mm, sufficient flame retardancy tends not to be achieved. On the other hand, when the thickness exceeds 3 mm, flame retardancy is facilitated, but for use purposes such as electronic device parts. There is a tendency to become unsuitable products.

  Such a sheet-like molded body can be cut as necessary, and can be easily attached to a portion requiring heat dissipation by making it into an arbitrary shape.

  Moreover, as hardness of such a sheet-like molded object, when measuring with an ASKER-C hardness meter, it is preferable that it is 10-45. When the hardness is less than 10, when the acrylic resin composition of the present invention is coated on, for example, a polyester film that has been subjected to silicone release treatment at the time of production of a sheet-like molded body, the resin is cured by heating and then cured for a predetermined time. Although it peels from a film, in the process made to peel from this polyester film, it exists in the tendency for the said acrylic resin composition to stick to the said polyester film, and to peel. On the other hand, if the hardness exceeds 45, the flexibility of the sheet-like molded body is reduced, and for example, when sticking to an electronic device or the like, air is likely to be mixed between the electronic device and the sheet-like molded body, There exists a tendency for the adhesiveness with the said electronic device to fall.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Examples 1-8 and Comparative Examples 1-7)
First, the acrylic copolymer shown in Table 1, the hardness adjusting agent shown in Table 3, and the metal hydroxide (thermally conductive filler) shown in Table 4 are blended in the proportions shown in Tables 5 and 6. The mixture was stirred to obtain a mixture. Next, after sufficiently defoaming the mixture, the curing agent shown in Table 2 (compound containing two or more glycidyl groups in one molecule as a functional group) is added to the mixture in the ratios shown in Tables 5 and 6. The mixture was stirred and degassed under reduced pressure to obtain a resin composition. Table 5 shows the content (mass basis) of the hardness adjusting agent with respect to the calculated amount of the hardness adjusting agent such that the functional group ratio calculated by equivalent calculation with respect to the acrylic copolymer is 1: 1. And in Table 6.

  Next, the acrylic resin composition thus obtained is coated on a polyester film whose surface is subjected to silicone release treatment, and then cured by heating in an oven at 190 ° C. for 13 minutes. Then, it was cured by leaving it at room temperature for 24 hours to obtain a sheet-like molded body.

  The following evaluation was performed on the sheet-like molded body thus obtained.

<Hardness measurement>
Using an ASKER-C hardness meter, the hardness of the sheet-like molded body of the present invention obtained in Examples 1 to 8 and the comparative sheet-like molded body obtained in Comparative Examples 1 to 7 were measured. The results are shown in Tables 5 and 6.

<Thermal conductivity>
Using a rapid thermal conductivity meter QTM-500 (manufactured by Kyoto Electronics Industry Co., Ltd.), the sheet-like molded body of the present invention obtained in Examples 1 to 8 and the sheet form as a comparison obtained in Comparative Examples 1 to 7 The thermal conductivity (unit: W / mK) of the molded body was measured. The results are shown in Tables 5 and 6.

<Adhesion>
First, using the sheet-like molded product of the present invention obtained in Examples 1 to 8 and the sheet-like molded product as a comparison obtained in Comparative Examples 1 to 7, the length was 4 cm, the width was 4 cm, and the thickness was 1.0 mm. Each sample was manufactured. Thereafter, each sample (4 cm × 4 cm) obtained as described above is sandwiched between two glass plates (6 cm long and 6 cm wide), and heated for 100 hours at a temperature of 100 ° C. under a load of 1 kg. Then, the mixed state of the air layer between the sample and the glass plate was observed. The evaluation criteria are as follows. The results are shown in Tables 5 and 6.

〔Evaluation criteria〕
A: No air layer is mixed. O: The air layer is mixed in a very small part. Δ: The air layer is partially mixed. X: The air layer is mixed in almost the entire surface.

<Processability>
The processability of the acrylic resin composition of the present invention obtained in Examples 1 to 8 and the comparative acrylic resin composition obtained in Comparative Examples 1 to 7 was evaluated. The evaluation criteria are as follows. The results are shown in Tables 5 and 6.

〔Evaluation criteria〕
A: The viscosity was low and kneading was possible, and sheeting was possible. ○: The viscosity was slightly high but kneading was possible, and sheeting was possible. Δ: High viscosity and kneading was somewhat difficult. X: It was somewhat difficult to form a sheet. X: Viscosity was high and kneading was difficult, and sheeting was also difficult.

  As is apparent from the results shown in Table 5 and Table 6, when the acrylic resin composition of the present invention is used (Examples 1 to 8), the processability is high, and the obtained sheet-like molded body is also flexible. It was confirmed that it was high and the adhesiveness was excellent. On the other hand, when the comparative acrylic resin composition was used (Comparative Examples 1 to 7), it was confirmed that the processability was low, and the obtained sheet-like molded body also had high hardness and low flexibility.

  As described above, according to the present invention, it is possible to improve the processability by sufficiently suppressing the viscosity, and to obtain a sheet-like molded body that has a high degree of flexibility and can be attached to an electrical component or the like with good adhesion. It is possible to provide an acrylic resin composition that can be used, and a sheet-like molded article obtained by using the acrylic resin composition.

  Therefore, since the sheet-like molded body of the present invention is excellent in flexibility and adhesion, heat generated from components such as electronic devices, for example, IC chips, CPU chips, GPU chips, etc., which generate heat locally, is radiated to a heat radiating part, such as a heat sink. It is useful as a sheet used for heat transfer.

Claims (2)

Contains an acrylic copolymer containing a carboxyl group as a functional group, a compound containing two or more glycidyl groups in one molecule as a functional group as a curing agent, and a monofunctional glycidyl group as a hardness modifier compounds and the a-containing child,
The hardness in an amount ranging from 1 to 60% on a mass basis with respect to the calculated amount of the hardness adjusting agent having a functional group ratio calculated by equivalent calculation of 1: 1 for the acrylic copolymer. Containing a conditioner; and
The compound containing a monofunctional glycidyl group as the hardness adjusting agent is an alcohol glycidyl ether or phenyl glycidyl ether having 4 to 15 carbon atoms,
An acrylic resin composition characterized by the above. A sheet-like molded article, wherein the acrylic resin composition according to claim 1 is molded and cured into a sheet.